首页
登录
职称英语
The ability of falling cats to right themselves in midair and land on their
The ability of falling cats to right themselves in midair and land on their
游客
2023-11-20
11
管理
问题
The ability of falling cats to right themselves in midair and land on their feet has been a source of wonder for ages. Biologists long regarded it as an example of 【C1】______ by natural selection, but for physicists it bordered on the miraculous. Newton’s laws of motion 【C2】______ that the total amount of spin of a body cannot change 【C3】______ an external torque speeds it up or slows it down. If a cat has no spin when it is released and experiences no external torque, it ought not to be able to 【C4】______ as it falls.
In the speed of its execution, the 【C5】______ of a tumbling cat resembles a magician’s trick. The gyrations of the cat in midair are 【C6】______ fast for the human eye to follow, so the process is obscured.【C7】______ the eye must be speeded up, or the cat’s fall slowed down for the phenomenon to be observed. A century ago the former was accomplished 【C8】______ high-speed photography using equipment now 【C9】______ in any pharmacy. But in the nineteenth century the 【C10】______ on film of a falling cat constituted a scientific experiment.
The experiment was described in a paper presented to the Paris Academy in 1894. Two sequences of twenty photographs【C11】______ one from the side and one from behind, 【C12】______ a white cat in the act of righting itself. Grainy and quaint 【C13】______ they are, the photos show that the cat was dropped upside down, with no initial spin, and still landed on its feet. Careful analysis of the photos reveals the secret. As the Cat rotates the front of its body 【C14】______ , the rear and tail twist counterclockwise, 【C15】______ the total spin remains zero, 【C16】______ Newton’s laws. Halfway down, the cat pulls in its legs before reversing its twist and then extends them again, 【C17】______ the desired end result. The explanation was that while no body can acquire spin without torque, a flexible one can readily change its 【C18】______ . Cats know this instinctively, but scientists could not be sure how it happened 【C19】______ they increased the speed of their 【C20】______ a thousandfold. [br] 【C19】
选项
A、unless
B、when
C、until
D、after
答案
C
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3204576.html
相关试题推荐
Inancienttimespeoplewhowerethoughttohavetheabilityto________dreams
Theywillneverreconcilethemselvesto________.A、defeatB、theirdefeatC、bede
[originaltext]Inadditiontothesegeneralthreatstostabilityandsecuri
Noonecandenythatpesticidehaveimprovedtheabilityoffarmerstobrin
Noonecandenythatpesticidehaveimprovedtheabilityoffarmerstobrin
Noonecandenythatpesticidehaveimprovedtheabilityoffarmerstobrin
Noonecandenythatpesticidehaveimprovedtheabilityoffarmerstobrin
Noonecandenythatpesticidehaveimprovedtheabilityoffarmerstobrin
Noonecandenythatpesticidehaveimprovedtheabilityoffarmerstobrin
Noonecandenythatpesticidehaveimprovedtheabilityoffarmerstobrin
随机试题
[originaltext] (5)InhisfirstbigspeechbeforeparliamenttheGreekPrimeM
Everyautumn,retailershirelargenumbersofseasonalworkerstohandlethe
A.心率加快 B.体循环静脉淤血 C.毛细血管通透性增高 D.肺淤血、肺水
个体发展的可能状态转化为现实状态的决定性因素是( )A.遗传因素 B.环境因
A.中药材B.中药饮片C.中成药D.中药E.天然药物药用植物、动物的药用部分采收
多元回归模型可能产生多重共线性的常见原因有()。A.变量之间有相反的变化趋势
下列关于酒剂与酊剂质量控制的叙述,正确的是A.酒剂不要求乙醇含量测定 B.酒剂
三叉神经痛首选的是 (常见症状的自我药疗)A.黄连素 B.乳果糖 C.苯丙
根据车辆购置税法律制度的规定,下列各项中,不属于车辆购置税征税范围的是()。A
广播电视建设项目采购的建筑材料、建筑构配件和设备,其包装上的标识应当符合()要
最新回复
(
0
)